Graduate School of Environmental Studies, Nagoya University, Furo, Chikusa, Nagoya 464-8601, Japan.
Niigata Field Station, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, Niigata, Niigata 961-8121, Japan.
Biol Lett. 2024 Aug;20(8):20240223. doi: 10.1098/rsbl.2024.0223. Epub 2024 Aug 7.
Marine predators often aggregate at the air-sea boundary layer to pursue shared prey. In such scenarios, seabirds are likely to benefit from underwater predators herding fish schools into tight clusters thereby enhancing seabirds' prey detectability and capture potential. However, this coexistence can lead to competition, affecting not only immediate foraging strategies but also their distribution and interspecies dynamics. We investigated both the longitudinal relationships and instantaneous interactions between streaked shearwaters () and common dolphinfish (), both preying on Japanese anchovy (). Using GPS data from 2011 to 2021, we calculated behavioural parameters for streaked shearwaters as an index of time spent and distance travelled. Despite the abundance of Japanese anchovies, we found that streaked shearwaters might increase their foraging time in the presence of underwater predators. Moreover, video loggers provided direct evidence of streaked shearwaters and common dolphinfish attacking the same fish schools, potentially interfering with bird foraging by dolphinfish. Our results suggest that the presence of underwater predators in a given patch might increase the time spent by seabirds foraging without affecting the distance travelled. This highlights the need for future studies that consider the potential adverse effects of other top predators on seabird prey availability.
海洋捕食者常在海气界面层聚集以捕食共同的猎物。在这种情况下,海鸟可能会受益于水下捕食者将鱼群驱赶成密集的鱼群,从而提高海鸟的猎物可探测性和捕食潜力。然而,这种共存可能会导致竞争,不仅影响捕食者的即时觅食策略,还会影响它们的分布和种间动态。我们研究了条纹海雀()和灰海豚()之间的纵向关系和瞬时相互作用,两者都捕食日本沙丁鱼()。利用 2011 年至 2021 年的 GPS 数据,我们计算了条纹海雀的行为参数,作为其觅食时间和旅行距离的指标。尽管日本沙丁鱼丰富,但我们发现条纹海雀在水下捕食者存在的情况下可能会增加觅食时间。此外,视频记录仪提供了条纹海雀和灰海豚攻击同一鱼群的直接证据,这可能会干扰海豚的觅食。我们的研究结果表明,在特定斑块中存在水下捕食者可能会增加海鸟觅食的时间,而不会影响其旅行距离。这突显了未来研究需要考虑其他顶级捕食者对海鸟猎物可获得性的潜在不利影响。